The overall objective of the proposed studies is to understand the mechanisms which regulate the continual exchange of cations and water between the crystalline lens and its environment. These mechanisms are essential to the cation and water balance of the lens and thus contribute to the maintenance of lens transparency. Ultimately, we hope to reach an understanding of the relationship between changes in lens cation and water balance and the development of human cataract. In the present project period, we will examine: (1) regulation of lens calcium content; (2) the role of calcium in maintaining lens membrane permeability properties; (3) basic electrical properties of lens memebranes; (4) lens changes in experimental hypocalcemic cataract and traumatic cataract; (5) developmental aspects of lens physiology.